In the previous post we learned how to launch the computer in the minimal configuration. Now lets see how it works in details.

MONITOR-0 which is responsible for the computer work in the minimal configuration is allocated in the ROM in the range 0000H-03FFH. To launch it we just need to reset the computer by “RESET” button (KEY[0] on DE1 board or ‘ESC’ button on PS/2 keyboard).

It is important that this ROM is turned on (switch SW[2] on DE1 board is in position “1”).

MONITOR-0 uses only few memory cells for stack and keeping temporary data. When MONITOR-0 is launched, the stack pointer is set up and “11” is shown on two right indicators. It means that the computer is waiting a command from the keypad.

As you remember, the extension board or PS/2 keyboard can be used for this purpose. Keypad is double functional – after initialisation each button is used to enter a command and then it is used to enter parameters. MONITOR-0 commands are listed in the sheet:

Key

Parameters

Description

0

ADR

Write data to RAM starting from ADR

1

–

Write data to RAM starting from C000H

2

–

Read data from RAM starting from C000H

3

–

Indicators test

4

–

RAM test

5

ADR

Read data from RAM starting from ADR

6

–

Launch program from C000H

7

ADR

Launch program from ADR

8

ADR1, ADR2

Control sum from ADR1 to ADR2

9

ADR1, ADR2

Record data from ADR1 to ADR2 on tape

A

ADR

Read data from tape with offset ADR

B

–

Time indication

C

ADR

Clock setup with ADR: C3FDH – seconds, C3FEH – minutes, C3FFH – hours

All MONITOR-0 commands are hex digits and contain up to three parameters. All parameters are in hex format as well. They should be entered straight after command.

Command “4” allows to test computer’s RAM. If it shows С400 on HL, then it means that there is no errors in RAM range from C000H to C3FFH. The test performs by writing and reading zeroes and ‘1’ to each memory cell. If any cell is malfunctioned, its address will be shown on HL indicator. Please be aware that all cells of this range will be filled with “1” after this test, so any preloaded program will be erased.

Command “1” allows to start data recording to RAM from C000H. After pressing “1′ button code С000 appears on HL indicators and code 00 on A indicator. Following keyentries record data to RAM. Entering data is displayed on A indicator and current cell address on HL indicators. The computer switches to the next cell with 1 second delay. So, if you keep holding “1” button, “1′ will be recorded to all cells from C000H.

Command “2” is to read data from memory cells from C000H address. After enetering the command the starting address С000 will appear on HL indicators. Indicator A will be showing the contents of the cell. By pressing any button you can go to the next cell.

Command “0” is similar to command “1”, but requires a parameter – the address from which the data have to be recorded to RAM. When you enter the parameter it is displayed on the indicator A, and when it is completed the address appears on the HL indicators. Indicator A displays 00. Now we can enter data for the next memory cell.

Command “5” allows to read data from any address. After “5” button has been pressed, an address parameter needs to be entered. It displays on A indicator. When completed it is displayed on HL indicators and A indicator contains data in the cell. The following cells can be reviewed by pressing any button.

There is another special command for operations with memory – command “Step back”. This command is not in the table above. It has a separate button “ШН” (KEY[3] on DE1 board or “TAB” button on PS/2 keyboard) and can be entered when abovementioned memory commands are in use. Lets say that a command of memory read is currently launched. Indicators HL show an address: «С003» and indicator A displays data in this cell: «22». If “Step back” (“ШН”) button is pressed, indicator A displays zeros and we are able to put a new data to the cell with С003Н address and following cells as well.

Command “8” calculates the control sum of a memory range. There are two parameters to be entered – start and end address of memory range for control sum calculation.

To write data on tape a command “9” is used. It has two parameters – first and the last address of memory range which needs to be recorderd. A tape recorder has to be turned on just before the last button is pressed, because data will be sent immidiatly. Recording speed is fixed at 1500 bit/sec. It records 256 bytes of 00 and then Е6 (sync byte). Then it sends low byte of start address, high byte of start address, low byte of end address, high byte of end address and finally goes the data. At the end, control sum of recorded data is displayed on HL indicators.

Command “А”» is used to read data from a tape. It has only one parameter – offset. If offset is 0000 then program will be read to the same range from which it was recorded. If a program has been read correctly, HL indicators will show correct control sum (the same as in write operation). The last button of the command needs to be pressed as soon as you hear the first sounds from the tape. There are two command to run programs.

Command “6” runs a program from address C000H.

Command “7” allows to run a program from an address that is entered as a command parameter. Command “7” can also be used to run some programs that are included in MONITOR-0 from address 0200Н to 03FFH. We will use it to run MONITOR-F of full configuration from address F800H as well.

Lets see what those programs are for.

Address 0200Н contains “Copy” program. Its parameters are the first and the last address of a range to be copied and the first address of the range where the data has to be copied to. Lets say that we want to copy MONITOR-0 from address 0100Н to 0120Н to RAM from address С100Н to С120Н. In this case the following buttons need to be pressed:

7 0200 0100 0120 С100

If the data is copied successfully, indicator A will display “11”. It means that MONITOR-0 is waiting for the next command.

To check copied data you can use another program that compares two ranges. Its address is 03В2Н. This program has three parameters as well: the first address of the first range, the last address of the first range and the first address of the second range.The following buttons need to be pressed to compare copied range from the previous example:

7 03B2 0100 0120 С100

If both ranges are the same, then “11” displays on indicator A and MONITOR-0 waits for the next command. Otherwise an address with error is displayed and you can change the data there straight away, if you like, and further comparison.

Most programs need to be corrected to run from a new address. It can be done with “Corrector” program. It starts from address 025FH. It has three parameters: the first and the last addresses of initial program and the first address of a copy. For our example the following buttons need to be pressed:

7 025F 0100 0120 С100

When the job is done “11” displays on indicator A and MONITOR-0 is ready for the next command.

If you want to use corrected program on another computer with addresses range different from “UT-88”, “Supercorrector” program can be used. It starts from 02Е5Н. It has the same parameters like “Corrector”. For our example, if we want to prepare the program to be able to run from address F100 the following buttons need to be pressed:

7 02Е5 С100 С120 F100

When the job is done “11” displays on indicator A and MONITOR-0 is ready for the next command.

Sometimes it is nesessary to insert or delete a byte in a program. There are three programs for this task.

“Insert byte” program starts from 035ЕН. Parameters are: address for a byte to be inserted and the last address of the program.

“Delete byte” program starts from 0388Н. Parameters are: address for a byte to be inserted and the last address of the program. Program finishes with review of the remainig part of the program.

“Change address” program starts from 0309Н. The first and the last addresses of the program, as well as old and new addresses, have to be entered as parameters. When the task is completed, “11” displays on indicator A and MONITOR-0 is ready for the next command.

The last standard program from MONITOR-0 is a program that displays CPU registers. It is very useful feature for debugging. To use it the following bytes need to be enterd to a program by “Insert byte”: CD DD 03. Your program will stop in this place and show the current address and its data. By pressing any button you can see CPU registers in the following order: AF, ВС, DE. The program runs further after that.

Command “3” tests 7-segment indicators of the computer. It chows hex digits from 0 to F to all indicators. MONITOR-0 has a clock program as well. There is a 1Hz timer interrupt that is used by this program. It can be turned on by switch SW[6].

Command “С” is used for time setup. After pressing “C” all interrupts are disabled. The address C3FDH needs to be entered and then seconds, minutes and hours are keyed in. To start the clocks “RESET” button has to be pressed (KEY[0] on DE1 or “Esc” on PS/2 keyboard). It will enable interrupts and start clock.

For time indication command “B” can be used. HL indicators display hours and minits, while indicator A displays seconds.

There were some games published in the “Young Technician” journal for this computer. For convenience I’ve put those programs to ROM which has an address range from 0200 to 23FF. This ROM can be switched on by SW[4] on DE1 board.

Program «Reaction» can be loaded from the ROM by the following command:

7 0200 2000 205F С000

(make sure that the ROM is turned on by SW[4] before) or loaded from a tape by command “1” from address C000H to C05DH. After launching the game with command “6”, press “0” and any button. All indicators will show “FF”. You have to press “RESET” button as soon as indicators change. A number on the indicators shows your reaction speed. Less is better.

Program «Gamma» can be loaded from the ROM by the following command:

7 0200 2060 20EF С000

or from a tape with command «1» from C000H to С082Н. To launch the program command “7” is used from address С03ЕН. After program launch, notes time and delay between them is enterd by hex figures in the range of 01-FFH. Gamma is played through “LINE OUT” jack.

Program «Noughts and crosses» can be loaded from the ROM by the command

7 0200 20F0 215F С000

or from the tape from addresses C000H to С065Н. Game field is consists from 9 cells as marked below:

01

02

03

08

09

04

07

06

05

When the game is launched by command “6”, on the right indicators “09” is displayed. It is the first move of the computer. In this game the computer always starts first with this move. Enter cell number to put your nought. If the computer wins it displays “73”, in case of draw – “11”.

Program «Labirinth». «Labirinth» is a field of 16 х 16 size filled with some obstacles. Set of obstacles needs to be loaded separatly starting from С200Н. Keeping the field in mind, a player have to go from the bottom right corner (coordinates FFH) of the field to the top left (coordinates 00H) corner by the shortest possible route. Moves are performed by four buttons: «1» — one cell left; «2» — one cell right; «3» — one cell up; «4» — one cell down. Each move combined with a short sound (through “LINE OUT” jack). If there is an obstacle, then no sound played but the step is counted. Number of moves is displayed on HL indicators while current coordinates are on indicator A. The game can be loaded from ROM with this command:

7 0200 2160 225F С000

or loaded from the tape from address C000H. Also the labirinth map has to be loaded from address С200Н. A tape can be used for this purpuse or it can be loaded from the ROM as well:

7 0200 2260 235F С200

After that the game can be launched with command “6”. Any button has to be pressed to start the game.

Math library

One of the computer extensions was a math library which allowed to calculate simple math operations as well as computing trigonometric, exponential and logarithmic functions. This library can use floating-point numbers.

I’ve added this library to the project as well. The library uses cells С361— C37F for baseline data, intermediate calculations and the final result. Baseline data is written in the form of single-byte and double-byte fixed-point numbers in the direct code. The sign of the number recorded in the highest bit. If it is “0”, the number is positive, if it is “1” – negative. For two-byte numbers the 15th bit contains the sign bit and 14th bit is an overflow bit. Single-byte can be from FFH to 7FH or from —127 to + 127. Double-byte — from BFFFH to 3FFFH (from -16 383 to +16 383).

For floating-point numbers a triple-byte numbers are used. The first byte determines an order of magnitude, while the second and the third – the mantissa. Binary number represented in the floating point format, can be calculated by the formula:

D = (-1)s * 2e (-1)p * f

where Р — sign bit of an order of magnitude, S—number sign bit (if S=0 — number is positive, if S = 1 — negative), е — order of magnitude, f — mantissa.

Order of magnitude shows the number of binary positions on which mantissa needs to be shifted to make a number in memory presented in the form of a normalised number, which is less than 1, with the first significant digit after the decimal point. If a sign bit of an order of magnititude is zero, mantissa shifts left. Othewise – right. Hence, the range of digits that can be shown is form 10-35 to 1035.

There are two types of programs in the math lab – main and service. Lets have a loon on service ones first.

Mantissa normalisation.

The first service program is “Mantissa normalisation”. Triple-byte number from memory С371Н, С372Н, С373Н is normilising by mantissa shifting. One bit right shift increases order of magnitude by 1, while one bit left shift decreases it by 1. As a result the cells will have a number in it with zero 14th mantissa bit and ‘1’ in 13th mantissa bit. Launch address for this program is 092DH.

Two numbers normalising.

This program does relative normalisation of two numbers. It needs, for instance, to sum floating-point numbers, which requires equal orders of magnitude. The program takes the first number from С371Н, С372Н, С373Н and the second number from С374Н, С375Н, С376Н and compares the absolute values of its orders of magnitude. Bigger order replaces smaller one and mantissa of the number with smaller order shifts right on orders difference between those two numbers. The launch address of this program is 0877Н.

Passing data to registers

This program passes triple-bit number to registers А — В — С. Initial address of this number has to be in regiter HL. The launch address of this program is 0А8СН. Another brogram passes data from registers А — В — С to memory using an address from HL register. The launch address of this program is 0А92Н.

Arithmetic operations

Addition of single-byte signed numbers.

The terms have to be located in addresses С371Н and С374Н. The result is put to address С374Н. The launch address is 0849Н.

Addition of double-byte signed numbers.

The terms have to be located in addresses С372Н and С373Н (the first term) and С375Н and С376Н (the second term). The result is put in to addresses С375Н and С376Н. The launch address is 08DDH.

Addition of trople-byte floating-point numbers.

The first term should be put in cells С371Н, С372Н, С373Н and the second term in cells С374Н, С375Н, С376Н,. The result will be in cells С374Н, С375Н, С376Н. The launch address is 0987Н.

Multiplication of two-byte signed numbers.

The factors are located in memory at the addresses С372Н, С373Н and С375Н, С376Н. The product is entered in cells С375Н, С376Н. The launch address is 0994Н.

Multiplication of trople-byte floating-point numbers.

The factors are located in memory at the addresses С371Н, С372Н, С373Н and С374Н, С375Н, С376Н. The product is entered in cells С374Н, С375Н and С376Н. The launch address is 09ЕСН.

The division of two-byte fixed-point numbers.

The dividend and divisor are located in memory at the addresses С375Н, С376Н and С372Н, С373Н. The result is in cells С375Н and С376Н. The launch address is 09F9H.

The devision of floating-point numbers.

The dividend is located in cells С374Н, С375Н, С376Н, the divisor in cells С371Н, С372Н, С373Н. The result is in cells С374Н, С375Н, С376Н. The launch address is OA6FH.

The exponential function.

The exponent is stored in the cell С364 and a power in cells С371Н, С372Н, С373Н. The result will be in cells С374Н, С375Н, С376Н. The launch address is 0В08Н.

The logarithmic function (natural logarithm).

An argument is entered in cells С361Н. С362Н, С363Н. The result will be in cells С368Н, С369Н, С36АН. The launch address is ОВ6ВН.

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